In Keratoconus, the cornea, thins and bulges forward, protruding outwards so that the contour becomes slightly pointed like a cone. Occasionally some scarring may occur in the centre as the cornea becomes further thinned and stretched. Extensive scarring can cause poor vision and a corneal graft may be required in some people. Usually however the condition can be managed with contact lenses.
The exact cause of keratoconus is unknown. It can sometimes be inherited, but often it arises spontaneously. People with hayfever, eczema and asthma appear to be more likely to develop it. In some people rubbing the eyes a lot may cause the cornea to become distorted.
The condition is usually first detected in early teenage years. It can then continue to progress and usually stabilizes around the mid twenties.
There is no cure for keratoconus, but a new treatment called collagen cross linking can help to strengthen the cornea and slow down or stop its progress.
Contact lenses are usually the best choice for improving vision. The irregular surface gives rise to an irregular prescription, usually with high degrees of astigmatism. Glasses may give acceptable vision in mild keratoconus, but more often than not, contact lenses that restore regularity to the corneal surface are required. Most people with kerataconus can continue to obtain good enough vision for most activities with contact lenses. Soft, hard and scleral lenses are available in keratoconic designs. If surgery or cross linking is indicated, contact lenses are usually fitted afterwards to further improve the vision and these are usually hard or scleral lenses.
Excellent information on keratoconus is available from the American Academy of Opthalmology website here